ADHD and diet
The diagnosis of Attention Deficit Hyperactivity Disorder (ADHD) is increasing in both the paediatric and adult population. ADHD is characterised by inattentive, hyperactive and impulsive behaviour that, for children, is present in more than one environment (ie home and school) and some of the criteria (see adhd.org.nz) is present before age 7.
In adults, the condition is characterised by a number of behavioural attributes, including an inability to focus or being hyper-focused or obsessive, setting unattainable goals and not being able to complete them, being tactless and impatient, finishing the sentences of others and being forgetful and unable to retain information.
Though we probably all experience moments like these in everyday life, if they characterise your behaviour then it is indicative of ADHD. People presenting with ADHD also experience other conditions such as eczema, allergies, asthma and gastrointestinal problems, which aligns with our increasing understanding of the interactions between our gut and our brain (the gut-brain axis).
Central nervous stimulants are the standard treatment for ADHD — increasing attention and reducing hyperactivity by altering neurotransmitter pathways in the brain — and they are effective in the short term. However, long term safety of their use isn’t known, and there are concerns around the impacts sustained use can have on the brain, given that neurotransmitters are involved in the development of the central nervous system (CNS). Many side-effects are reported, including abdominal pain, insomnia and weight loss.
This highlights the need for more information around effective alternative (or adjunct) therapies to help manage ADHD symptoms. The use of nutrients and specific diets have received attention in this realm. Specifically, research comparing the nutritional status of those with ADHD to those without it has uncovered many interesting relationships between certain nutrients, dietary patterns, food constituents, food groups and ADHD. While these types of studies cannot determine cause and effect (ie the lack of a nutrient being the cause of the disease), researchers hope it may point to using nutrition as a therapy for the management of ADHD symptoms.
Observational studies have found levels of certain nutrients, including zinc, iron, magnesium, vitamin D and omega 3 essential fatty acids are lower in people with ADHD than in the general population. All five nutrients play important roles in the structure and function of the CNS, and help regulate the immune system by controlling inflammation and oxidative stress in the brain, both of which are higher in those with ADHD. Despite that, studies that use supplements to increase these nutrients via single nutrient studies have shown mixed results, with regards to symptom management.
However, New Zealand research investigating multivitamin and mineral supplementation have found reduced aggression and improved self-regulation in both adults and children with ADHD.
High consumption of sugarsweetened beverages is associated with three times the risk of being diagnosed with ADHD.
Kimchi, bone fish and grains
A Japanese study found that a "healthy" diet pattern, characterised by kimchi, bone fish (meaning fish that you eat with the bones in, e.g. tinned sardines) and grains, lowered the odds of being diagnosed with ADHD. The bone fish would likely contribute to omega 3 and zinc status, and the kimchi (fermented cabbage) contributes beneficial bacteria to the gut and may help modulate the immune response and subsequent inflammation and oxidative stress.
Laboratory studies have determined ADHD could arise from mitochondria dysfunction in the brain, increasing oxidative stress and an inability for our brain to utilise glucose as a fuel source. This also changes the activity of neurotransmitters in the brain, notably serotonin, affecting behaviour and cognition around impulsivity.
This could point to the potential use of ketone bodies as an alternative fuel source, produced by the body as a by-product of a ketogenic diet (whereby 70 per cent or more of the calories come from fat). To the best of my knowledge this hasn’t been tested in the research environment, however there are reports of a ketogenic diet (used therapeutically for seizure control) also reducing ADHD-like symptoms in those with epilepsy.
Food additives, salicylates and highly allergenic foods
Artificial colours and flavours found in ultra-processed foods have also been investigated for their role in triggering ADHD symptoms. Elimination diets are often used to determine if the removal of food groups or food constituents (such as aforementioned additives, and natural and chemically occurring salicylates) can manage symptoms. This originated from the observations of a paediatrician and allergist in the US who saw children in his clinic presenting with allergy and ADHD symptoms. Naturally occurring salicylates are found in a wide variety of plant foods, including fruits, vegetables, herbs, spices and some nuts and seeds. They are also found in cleaning and skincare products and common medications such as aspirin. It is thought that salicylates influence ADHD symptoms either through an allergenic or pharmacologic mechanism. Elimination diets that remove highly allergenic foods (such as cow’s milk, gluten, eggs, chocolate and nuts) are also tested, due to the immune response, as it is suggested that ADHD has an immune-related imbalance (which can in part explain the co-occurrence of ADHD and gutrelated issues).
Though anecdotally there are many reports of improvements when specific food groups are removed, there is little to support this approach as a broad recommendation for all people with ADHDlike symptoms. This may be due to methodological challenges, as there are few well-designed clinical trials with numbers large enough to establish significant relationships. In addition, improvements are usually reported at a group level, which means individual responses to dietary changes can be missed.
Anecdotal improvement may well be due to an overall dietary change and not just the food group being eliminated. Removing ultra-processed food (which contains many of the added flavourings, preservatives and colours) brings with it an opportunity to increase or introduce other foods. For many, this increases the overall nutrient density of the diet and potentially the nutrient status of those with ADHD. Removing foods which contain phytates that bind iron (such as cereal-based products) may well increase iron and zinc availability, improving symptomology. There may be an increase in quality animal protein in the diet, thus an increase in iron, zinc and omega 3 that is consumed through the diet.
Many practitioners believe (and I agree) that optimising nutrient density in the diet is an avenue worth exploring to determine if dietary changes do improve symptoms associated with ADHD. With any dietary change, it is recommended you work with a nutrition practitioner and your medical professional in an integrated fashion to determine that nutrient needs are met, as it can be a challenge to support all requirements when following a restricted diet.